It is amazing what people put on the Internet, I was browsing around yesterday for a spiked flipper weapon and found this:
This was just what we needed for our robot, and it can be scaled up, the only problem is getting the right parts, especially the springs, if they are too small or too large then the entire weapon could break, plus we need to fit 3 of them in, angle all of them correctly, add the speed controllers then finally code it to a specific button or switch. I'm currently making a cardboard model to the exact size (resistant Materials really pays off) from our sketches, then finally make a CAD design and get too work.

Thanks for the support
Many thanks
Doodle